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ENGR5003 / Week 1
Lecture 2 exercise - surface-tension work on a bubbleTutorialCurrent specThird5 min

ENGR5003 Lecture 2 student exercise 3 (slide 12)

As a spherical bubble of ammonia vapour rises in liquid ammonia, its diameter changes from 5 mm to 25 mm. If the surface tension of ammonia is 0.02 N/m0.02\ \mathrm{N/m}, calculate the work done by the system to enlarge this bubble.

Formulas you may need
  • Surface-tension work: dW=σs dAdW = \sigma_s\,dA (on the formula sheet, forms of mechanical work)
  • Surface area of a sphere: A=πD2A = \pi D^2 (learn this)